The field of the invention relates to preservation methods for bacterial cultures. In particular, the field of the invention relates to preservation methods for methanogenic, hydrogen-utilizing cultures.
Methane is a commercially valuable fuel, as well as synthetic precursor, and can be obtained via microbial fermentation processes. In addition, proper methane production is required for stabilization of municipal, industrial and agricultural wastes via anaerobic digestion. Many euryarchaeotal microorganisms can use hydrogen and carbon dioxide to produce methane. These hydrogenotrophic methanogens are critical to proper functioning of most anaerobic digester systems in which complex substrates are broken down to simpler molecules, such as hydrogen, that are then converted to the final product, methane. If hydrogen utilization slows or stops, the entire biological system can be inhibited or may stop, resulting in an inoperable digester system. In addition, hydrogenotrophs are important in some soil and other environments.
Anaerobic digester systems, agricultural soil, or other environments may be improved if hydrogenotrophs are added. Unfortunately, preserving these organisms can be difficult since they are typically strict anaerobes, and even traces of oxygen are assumed to be toxic to them. In addition, they are thought to be very sensitive to temperatures above about 70 degrees Celcius, and to drying/dessication. On the other hand, it would be beneficial if hydrogenotrophic methanogens could withstand oxygen, and could be heat dried in an air atmosphere and stored in powder or solid form. The powder or solid may also contain protectants and bulking agents. Air drying would potentially be much more economical than freeze drying or other preservation methods. However, the conventional wisdom in the field is that hydrogenotrophs are very sensitive, and would therefore not survive air drying with or without heat in an air atmosphere.
Described herein is a method for preservation of methanogenic cultures, including hydrogenotrophs, by air drying with or without heating. The cultures may be rehydrated with an aqueous solution and utilized to bioaugment anaerobic digester systems to improve production of methane.